Tough choice ... there are good and bad in both boards. Both have great drums, but the Ketron patterns have a country "edge".
The Korg has better piano's and electric pianos. The Ketron has a better harmonizer. Better play them both ALOT first. It's like choosing a Caddilac or a Lincoln - both pretty fine choices.
Everyone, and everything I listen to is my teacher. Every instrument, every voice, every sound in nature ... they are all my private tutor ... 24/7 for free.